1. Field of the Invention
The present invention relates to an information processing apparatus, an information processing method and a program.
2. Description of the Related Art
In recent years, a video-recording/playback apparatus recording programs broadcasted by TV broadcast as digital data in a recording medium having random access capability such as a DVD (Digital Versatile Disc) or an HDD (Hard Disk Drive) has rapidly become widespread. Further, distribution of contents such as video and audio through the Internet has become popular, and a playback apparatus with a built-in HDD or flash memory is already widespread with which it is made possible to enjoy the contents downloaded from the Internet indoors and outdoors.
The playback apparatus for digital content as described above is implemented with various functions using characteristics of digital and random access. A variable speed playback function may be taken as an example which variably sets the playback speed while maintaining a constant pitch of a sound. The variable speed playback function is a function of slowing or speeding up the playback speed of video and audio, and the function slows the playback speed by around 20 percent for a person beginning to learn a language and the like (slow playback) or speeds up the playback speed by around 50 percent to save the time of viewing and the like (fast playback), for example. The variable playback function is a function that has been popularly implemented in a digital content playback apparatus since the beginning of the spread of the apparatus, and today, it has become quite common. The present invention focuses not only on audio content, but also on the audio part of the video content.
The technology of variably setting the playback speed while maintaining a constant pitch of a sound in a playback apparatus of digital content is called an speech rate conversion. Hereinafter, the speech rate conversion will mean a conversion of expanding or compressing a signal while maintaining a constant pitch of a sound. Several methods are known for the speech rate conversion, for example, the PICOLA (Pointer Interval Control OverLap and Add) serving as a time-axis expansion/compression algorithm at a time domain corresponding to a digital audio signal (see “Expansion/compression on the audio time-axis using duplication adding method by pointer amount-of-movement control (PICOLA) and its evaluation”, by Morita and Itakura, Acoustic Society of Japan collected papers, October 1986, pp. 149-150). This algorithm has an advantage in that though its processing is simple and lightweight, good sound quality can be obtained.